Viewbox disappears on restoring the WPF window down

Viewbox disappears on restoring the WPF window down

I have a Viewbox Control that contains a WindowsFormsHost which in turn
acts as a container to display images.
<Viewbox Grid.Row="1" Grid.Column="1" Stretch="Fill" MinHeight="50"
MinWidth="50">
<WindowsFormsHost Width="100" Height="100" Name="ImageSegment"
Background="Black"/>
</Viewbox>
With the above code, the ViewBox appears and resizes accordingly. But the
Viewbox disappears once it is restored down to a below specified Width.
<Viewbox Grid.Row="1" Grid.Column="1" Stretch="Fill" Height="875"
Width="975">
<WindowsFormsHost Width="100" Height="100" Name="ImageSegment"
Background="Black"/>
</Viewbox>
If i give it this way, Viewbox stays, but its auto-scaling property is
lost. Is there a way to get around this problem? Why it occurs? Thanks in
Advance!